Disclosed is a system and method for non-invasive corrosion detection, and more specifically, detecting metal corrosion using Passive Inter-Modulation (PIM) generated by multi-tone radio signals flowing through galvanic corrosion junctions.
Corrosion is a significant problem for both military and commercial systems. Corrosion can cause structural failure of the corroded member. In electronic equipment, corrosion can distort or disrupt the electrical signal that propagates through a metallic connector, that is, a conductor susceptible to corrosion. Corrosion is also a significant source of Electromagnetic Interference that can disrupt nearby systems. Damaging levels of corrosion can be hard to detect because the corrosion may be inaccessible or imperceptible on visual inspection. The effect of corrosion on electrical transmission is generally not linear.
Periodic testing to detect and apply early structural corrosion prevention measures can provide an enormous safety and cost benefit. Unfortunately, highly reliable corrosion detection methods do not exist to allow inspection of complex closed structures, which are unique because they require extensive disassembly or destructive testing, both expensive and undesirable methods.
The prior art systems and methods are directed to inducing circulating currents in a unit under test (UUT) with an antenna generated electro-magnetic field. Another antenna is used to sense the response. The problem with such systems is that the EM field is not easily confined without expensive Faraday cages because the radiation propagates everywhere. Appropriately, the FCC regulates the use of such methods and systems, which add additional complexity and expense to the tests. Furthermore, such systems and methods are not precise given the width of a radiating antenna pattern. This means that it is time consuming to narrow down with any degree of precision the location of the corrosion.
Devising a means of detecting and locating corrosion via simple application of radio signals that flow through closed structures would be of enormous economic benefit.